A friction clutch or brake includes an engaging member having a friction surface that wears over the life of the device. In order for the friction torque device to continue operating effectively, the relative position of the engaging members must be adjusted or realigned to compensate for wear that occurs on the friction surface.
More specifically, in a friction clutch, torque is transmitted from a driving member to a driven member, each member rotating about an axis. The driven member is interposed between the driving member and a pressure plate. In normal operation, a release assembly cooperates with the pressure plate to selectively move the pressure plate axially towards the driven member in order to engage and disengage the clutch. As wear occurs on a friction surface of the driven member, the pressure plate must be moved an additional axial increment to engage the driven member with the driving member. The relative position of the pressure plate must therefore be compensated internally for this additional increment of movement.
With most heavy duty friction clutches, the adjustment of a release bearing and spring assembly is manually achieved in order to compensate for wear on the friction surface of the driven member. Manual adjustment, however, requires continuous monitoring to determine if adjustment is necessary, as well as manpower to perform the adjustment. If the adjustment is not completed timely, the clutch will operate less effectively.
It is also known in the art to provide a clutch with an automatic adjustment mechanism. While a number of such mechanisms do compensate for wear, numerous parts are typically required for the desired result. Further, the operative parts are frequently disposed outside the cover of the clutch, thereby subjecting the parts to possible damage and an increased likelihood of breakdown. More significantly, prior art automatic adjustment mechanisms often do not fully, or timely compensate for wear on the friction surface. This is due, in part, to incomplete adjustment, or delayed adjustment after the friction surface has worn.
Accordingly, a need exists to provide a friction torque device with an automatic adjustment mechanism which has a simple structure with a minimum of interconnected parts, wherein the parts are disposed within a housing or cover for the device. A desirable adjustment mechanism may also provide an automatic adjustment mechanism that directly and effectively adjusts the friction torque device during normal operation while not reducing the operability of the clutch. The self-adjusting clutch may also have enduring performance when subjected to the frequent and rapid actuations prevalent with transmissions having automated shifting.